This invention relates to a novel use of electromagnetic energy in coffee technology. In particular, this invention pertains to the drying of decaffeinated green coffee beans utilizing electromagnetic energy within the frequency range commonly referred to as radio frequency heating. The use of this technology with decaffeinated green coffee beans has not only been found to effect a more rapid and uniform drying of the coffee bean but more importantly, results in a decaffeinated coffee product of improved flavor quality.
Heretofore, it has commonly been the practice to use various methods of air drying for drying decaffeinated coffee beans. Generally, the operating conditions common to the majority of such methods involves heating the air and passage of the same through a bed of coffee. Since coffee is granular, whether natural or washed, minimal resistance is offered to the passage of air, yet there is a sufficient amount of resistance to insure adequate heat and moisture exchange between air and coffee as well as even distribution of air flow to all parts of the bed. The method of through-circulation drying has been in the past, far more efficient as to heat and moisture exchange than merely passing the air over the surface of the coffee beans. For this reason, the coffee beans are usually kept in motion in order to effect more even drying.
A commonly used apparatus which functions to cause more uniform drying of the coffee bean is the Roto-louver dryer which, while drying the beans by air flow through louvers in the walls of the cylindrically-shaped apparatus, constantly mixes the beans by its rotary operation (Chemical Engineer's Handbook, John H. Perry, ed., McGraw-Hill Book Co., Inc., 1950, p. 825).
The vertical turbodryer is an additional type of dryer used in the coffee industry and demonstrates a procedure similar to the Roto-louver dryer. However, the vertical turbodryer, a type of continuous tray dryer, accomplishes a purportedly uniform drying by utilizing vertically arranged trays over which separate and continuous air flow is directed. The coffee beans are fed into the top tray and systematically introduced to progressively lower levels where further reduction of moisture content is achieved (Chemical Engineering Handbook, John H. Perry, ed., McGraw-Hill Book Co., Inc., 1950, p. 822).
As is evident from the discussion concerning conventional drying methods and the equipment available to accomplish the same, the current procedures involve refined equipment and extensive use of time and manpower in order to accomplish adequate drying of the bean. In addition, in utilizing the conventional drying methods the full flavor potential of the dried beans has not been realized as is evident from the improved flavor quality of the product of this invention.
The potentialities of the moderate frequency microwave type of electromagnetic energy for use in the heating and cooking of foods have been known for almost three decades but such technology as applied to the food industry for food processing and development is a relatively new innovation due to the previous unavailability of large-scale industrial apparatus.
Currently, electromagnetic energy of microwave wavelengths is being applied throughout the food industry for cooking, puffing of dry products such as fruits, thawing of meats and baked goods, and for drying of blanched products such as almonds where rapid removal of excess moisture is effected without adversely overheating the nut (An Introduction to the Industrial Applications of Microwave Energy, Varian/Industrial Microwave Operation, Palo Alto, California, July 1968, p. 28).
More recently it was found that the combination of microwave technology and the use of other type of drying processes such as the fluidized-bed were useful for drying such products as grains, vegetables, berries and the like (U.S. Pat. No. 3,528,179 issued Sept. 15, 1970),
Ideally, a method of drying decaffeinated coffee beans which not only accomplished a far more rapid and uniform drying of the bean, and eliminated the problem of combustion of the residual chaff and the like, but which at the same time produced a product with significantly improved flavor would be beneficial to both the industry and consumer at large. This invention affords a method of producing such a product by utilizing radio frequency heating to dry decaffeinated coffee beans.